Lightning-arrester.



PATENTED JULY 21, 1908.

R. D. MERSHON. LIGHTNING ARRESTER.

APPLICATION FILED SEPT. 27, 1904. RENEWED JULY 16, 1906.

Z'SHEBTS-SHEET 1.

- v Fig.1

Fig, 2

5454 did ,MLM

1V0. 893,712. PATENTED JULY 21, 1908.:

R, 31 MERfiHON.

LIGHTNING ARRESTER.

APPLICATION PILED'SEPT. 27, 1904. RENEWED JULY 16, 1906.

:xdd ldd unrrnn .raras onirrCE- RALPH D. MERSHON, OF NEW YORK, N. Y., ASSIGNOR TO THE WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

' LIGTiCTNZNG-ARRESTER.

Mascaras.

Specification of Letters Patent.

Patented July 21, 1908.

Application filed September 27, 1904, Serial No. 226,103. Renewed July 16, 1906. Serial No. 326,498.

To all whom it may concern: v

Be it known that vI, RALPH D. MERSHON, a citizen of the United States, residing at New York, in the county and State of- New York, have invented certain new and useful Improvements in Lightning-Arresters, of which the following is a specification, reference being had to the drawing accompanying and forming part of the same.

One of the most serious problems met with in electric power transmission is the protec tion of the lines and apparatus connected therewith from the destructive effects of lightning and other static disturbances, such as might follow the interruption of a circuit, etc., and the prevention of after disturbances of the system. A large variety of lightning arresters have been proposed and have been found more or less successful in practice. My invention, however, possesses certain advantages which have not. been found in the prior devices with which I am familiar. Those now in use, especially those for use on high voltage circuits, will take light discharges and successfully interrupt the dy namo current which follows, but they are inadequate for dealing with heavy discharges. One of the principal reasons for this ineffectiveness is that in order for'them to successfully interrupt the generator'current thereis usually included in series with the arrester a resistance to limit the current which follows the discharge. This resistance, in order to be effective for limiting the generator current, is given so high a value that a very heavy discharge cannot readily-pass through it, resulting in a piling up of potential at the time of such heavy dischargeQ If the resistance be given a lower value, to permit heavydischarges to pass, resulting in'a conseqkixiently greater disturbance on account of t e dynamo current which follows, then this greater disturbance will occur with all dis- V charges bot'h light and heavy.

It istt ge object of my invention to provide protecting devices which shall not only take care of the lightning discharge, thus saving theacostly apparatus of the system from injury, but also-such as will cause the disturbances to the system, due to; the dynamo cur rent which follows the discharge, to be proportional, or approximately so, to the necessities of the case. That is, where.. the

-lightning or other static discharge is small,-

the. after efiects upon the system will be bodiments.

paratively: small static disturbance.

slight, while considerable disturbances will be caused only by heavy discharges from which-the apparatus must be protected at any cost of after disturbance.

In carrying out my invention I provide a plurality of arresters connected to the ground independently or through portions of com- 5 mon resistance, of. such character, and so proportioned as to their reslstance as to provide paths suited for lightning discharges or other static disturbances of v'ariousmaghitudes and to permit the following of dynamo current only in more or less direct proportion to the magnitude of the discharge.

The invention will be more readily understood by referring to the accompanying drawings, in which Figurel is a diagram showing the preferred form. Fig/2 is a modification, and Figs. 3, 4, and 5 show other convenient cm- In Fig. 1 are shown two series of four ar-' rosters, a, b, c, d, of the well known horn type, each series connected to one of the line conductors Z, Z. Y The first of these devices indicated by a, is adapted to take care of,a

light discharge, and the arcing gap between the horns is. therefore narrow. The device is connected to'the ground G through a comparatively large resistance r. In the remaining, devices, which may be one, two, three or more, in number, the horns are spaced farther apart successively, and are connected with successively lower resistances, as shown, the last being preferably connected directly to the ground. The first pair of horns are so spaced that the dielectricv between them will be broken down by a com- The arc resulting from the dynamo current following the dischar e will tend to be put out by rising between t 1e divergent horns and by the high resistance in series with them, and the path to the ground thereby broken. However, if the arc persists, the resistance r and the rising of the arc on the horns will effectually limit the amount of the relativel low tension dynamo'current which can f0 low, giving the are time enou h to rise upon the horns until it is extinguis ed.- The disturbance due to flow of dynamo current is thereforeslight, and not infrequently is inappreciable. If the discharge is more violent,,to take care of it properly so as to prevent damage to the-apparatus onthe ine electroniotive force which it is desired they shall take care of, and which are connected by .lig

to the ground through a lower'resistance' than is used with thdcvice (L. Both dev1ces,'(t I) are therefore in operation simultaneously. in this case, if the are or .arcs persist, the lower resistance connected with the horns will of course permit a larger flow of dynamo current, but the apparatus on the line will be protected from injury. With a still more violent bolt the device 0 will come into operation, and for an instant all three will be discharging. The horns of the device 0 are stillfarther separated and the resistance to groundstill lower. The combined action of the three devices protects the ap aratus (this time from a discharge whi though at a cost of greater disturbance to the system if the are or arcs do not go out immediately. Finally the fourth pair of horns, d, fartherseparated than any 'of the others, are connected directly to the ground, or through very low resistance.

are so spaced that the dielectric between themivill be broken down only when the maximum voltage, which. the system can wwthstand without ni ury', .is exceeded, as er discharge. In the d is also included an au tornatic as L fuse f, or any other convenient dc" c. This last arrester protects the system from extremely powerful discharges, but of course the absence or comparative absence of resistance would allow proportionally greater flow of dynamo current. The effect might even be practically or quite equal to a short circuit. Before the latter could cause any damage, however, it is intended that the circuit to ground ring or otl.

circuit 0:

:tlnough the last pair of horns should be broken by the fuse or other device by the heavy dynamo current following the lightning discharge. The last arrester therefore operates as a sort of =1. ety VttlX'Q to take care of extraordinary conditions which might otherwise cause damage tn the apparatus which would entail nmch more serious loss a -.i annoyance than would the comparatively biiei disturbance of the system due to the heavy flow oi dynamo current and subsequent operation oi the i use or other devicef.

As stated before, any number of arresters may be used. l lxtraordinary precautions may require a considerably larger number than I have shown. Also, each or any of the arresters may be provided with a circuit breaker, as a fuse or other device, if desired, so as to open the ground circuit if the arc is very persistentv and the current flow from the might .otherwise wreck it) These horns dynamo considerable. lit will be understood,

01" course, that the line Wires, whether two, three or more in number, are each protected bya system of arresters. It is evident that the resistances employed in series with the discharge gaps need not necessarily be in any manner proportional to the width of the spark gaps themselves bu t. ma y ha ve any other value. For instance, the resistances ma y be equal. In this case the various dischz'irge gaps would still have the consecutive and cumulative action which CllilltlOilCIlZQS the invention, valthough the protective effect would not increase so rapidly with the successive breakdown of the gaps as with resistances proportioned as described above.

The system of protecting devices shown in Fig. 2 has automatic circuit breaking devices, as shown, in all the ground circuits, in lieu of resistances. It has, however, the same advantages of cumulative and con secutive operation the arrangement just described, and in addition the advantage that all the paths to earth are of very low resistance, though it possesses one feature which under certain circumstances may he a drawback, in that for the lighter discharges disturbance to the system will be greater than if the consequent dynamo current were limited by resistance. Each one ol the discharge paths shown in this figure is supposed to have low an ohmic resistance as pi ible. The .ohmic resistance of the dischar e path to ground may be reduced by increa ng the total. efiective cross section. of the path; but the inductive resistance ol the path cannot be materially reduced by incr sing its ()[Unrj section.

If it is desired to diminish the inductlve resistance the path must be subdivided, or duplicated, in multiple, as is done in the figure referred to. It is evident that this reduction of the inductive resistance accompanies also, to a greater or less extent, the other devices which are described herein,

especiallywherc each discharge gap has its own separate path to the groinn'i, as in the case of Fig. 3. It will of course be understood that both line wi or .legs" oi the circuit in Figs. 2 and 3 are to he provided with protecting devices, as in Fig. 1.

From the foregoing explanation it will he noted that the essence of my invention resides in the use of a plurality of devices oi successively higher striking potentials connected to ground, so constructed and arranged, as herein described, that the resultant disturbance to the system proportiona only to. the necessity of the case. \Yhcrc resistances are used they may be of values successively lower, corresponding to the successively higher striking clectromotivc foltcs of the devices. I

In Fig. 4 the similar ar'resters (I' (l b w, cc for the difl'erent line conductors are connected to common grounds G, G, G,

Git-G min Fig. 2. i g-C ils h, it, which and have independent resistance r, r, the devices'being provided with fuses f,f'. or other automatic circuit breakers. I 5, the ordinary saw-toothed deivic'esci, 12,are used instead of horns, connected-to the line conductors Z, Z, and ground Fig. 5 also shows chokmay of course beaused With-the othen'arrangemen'ts if desired. The lastdevice has'ghises or other-circuit breakers f, as in the embodiments previously described.

I am awarathat' it has been proposed heretofore to employ two or more arresters of different striking potentials, and I therefore not claim that idea broadly as my invention. So'far as I am aware, however, the

priordevices' of that character have all employ'e'd reactance or resistance between ,the

ductor may roduce of itself. to.

various aths to ground. I prefer to use no artlficia reactance and resistance between the various discharge paths, since I have discovered that it in general, desirable that the reactance and reslstance be m1n1mum that is, 'that the self-induction and resistance between the discharge paths be only such unavoidable amount as, for example in the arrangement shown in Fig. 1, the line con-- This may be made so sm'a has to be practically negligible,

"so that it may be said that there is substantially no inductance or resistance between the paths. This feature is expressed in the appended claimsby the statement that the connections from path to path on the system ,side are of low reactance and resistance, in

clude artificial reactance or resistance.

contradistinctionto connections which in- The object of keeping the reactance and resistance as low as possible is to make the conditions such-that all the, paths will be subjectedto substantially the same potential. The

gap of lowest striking potential will then (break down first, followed by as many more of higher striking potentials as may be nec essary to take care of the discharge. I

The invention is of course apphc able not only't'o transmission systems, but also to any other electrical-'sys tem which it is desired to protect from static disturbances, and to any part of the same, and may be embodied in a variety of forms without departing from its proper scope.

What I claim is: c

1. The combination with an electric line conductor, of a series of grounded discharge paths spaced apart and connected to said line conductor in multiple and severally provided with discharge gaps of successively higher striking potentials, the connections on the lineside of the gaps being of low reactance and-resistance, in contrad stinct on to con nections which include artificial reactanoe and resistance, as set forth. v c I .2. The combination w th an electric l ne paths conductor, of a series of grounded discharge paths spaced apart and connected to said line conductor in multiple and severally provided conductor ,in multiple and severally provided with discharge gaps of successively higher striking potentials and with successively lower resistances between ground, 'as set forth. 7

4. The combination with an electric line conductor, of a series of grounded discharge paths spaced apart and connected to said line conductor in multiple and severally provided with discharge gaps of successively higher striking potentials and with successively less amounts of a common artificial resistance in all but one of said paths, as set forth.

5. The combination with an electric line conductor, of a series of grounded discharge paths spaced apart and connected to said line conductorin multiple and severally provided with discharge gaps of successively higher striking potentials, the connections to the line conductor being of low reactance and resistance, 1n contradlstmctlon to connections which include artificial'reactance or resist-- ance, and automatic circuit-breal 1ingmeans in one or more of the paths, as set lorth.

6'. The combination with an electric line conductor, of a series of grounded discharge paths spaced apart and connected to said line conductor in Inultiple'and severally provided with discharge gaps of successively higher striking potentials and with succes- ,.sively lower resistances between the gaps and the ground, and automatic circuit-breaking means in one or more ofthe paths, as set forth.

'7. The combination with an electric line conductor, of a series of grounded discharge aths spaced apart and connected to said line conductor in'multiple and severally provided with discharge gaps-of successively higher striking potentials and with successively less amounts of a common artificial resistance in all but one of the paths, and automatic c1rcu1t-break1ng means in one or more ofithe paths, as set forth.

8. The combinationwith anelectric line conductor, of a series of grounded discharge paths spaced apart and connected to said line conductor in multiple and severally provided with discharge gaps. of successively higher striking potentials and with successively lower amounts of resistance between the gaps and the ground, and automatic cirg the gaps and the cuit-ln'eaking means in the path having the discharge gap of highest striking potential, as set forth.

9. The combination with an electric line conductor, of a series of grounded discharge paths spaced apart and connected to said line conductor in multiple and severally provided with discharge gaps of successively higher striking potentials and with successively less amounts of a common artificial resistance in all but one of the paths, and

automatic circuit-breaking means in the the respective gaps and the ground.

12. In a protective system for electrical circuits, a series of discharge gaps of different striking potentials spaced apart and inter-' posed between the line to be protected and the ground, and non-inductive resistances of difi'erent values interposed between the gaps and the ground.

13. In a protective system for electrical circuits, a series of discharge gaps of different striking potentials spaced apart and interposed between the line to be protected and the ground, and resistances interposed between the gaps and the ground, the values of which are inversely proportional to-v .the

v striking potentials of the gaps to which they are connected.

14. In a protective system for electrical circuits, a series of paths spaced apart and.

interposed between the line to be protected and the ground and respectivelycomprising discharge gaps and resistances of different values upon one'side only of the gaps.

15. In a protective system for electrical circuits, a series of paths spaced apart and interposed between the line to be protected and the ground and respectively comprising discharge gaps and resistances of dlfferent values between successive adjacent gaps upon one side only thereof. 16. In a protective system for electrical circuits, a series of paths spaced apart and interposed between substantially equi-potential points of the line to be protected-and the ground and respectively comprising discharge gaps of different striking otentials and resistances upon one side 0 y of the gaps.

17. In a protective system for electrical circuits, a series of discharge gas spaced apart and interposedbetween the ine to be protected and the ground, and resistances of different values between the grounded terminals only of successive adjacent gaps.

18. In a protective system for electrical circuits, a series of discharge gaps spaced apart and interposed between the protected and the ground, and-resistance paths of different values between the grounded terminals only of the respective gaps and the ground. j

RALPH .D. MERSHON. Witnesses:

S. S. DUNHAM, M. Lawson DYER. 

